If copying large files you might want to consider 'how'.
It comes down to Buffered vs. Unbuffered Input/Output (I/O).
Unbuffered copies are built-in to Win 2008 R2 and the Win 7 version
To perform unbuffered copies on an older system the following tools are useful.
FastCopy - Download
Eseutil (exchange install) - Download
How to copy very large files across a slow or unreliable network